The present invention refers to a method and apparatus for measuring true slab surface temperature in a reheat furnace, more particularly utilizing one or more pyrometers.
U.S. Pat. No. 4,144,758 of John E. Roney discloses a furnace with a steel slab being heated. One pyrometer is trained on the slab and a second pyrometer detects radiation from a reference plate mounted on the wall. A temperature sensor is mounted within the furnace wall. Outputs of the pyrometers are subtracted at a summing junction. Some of these features are found in the present invention but changes from this in the apparatus and the method of the present invention allow optimization of reheat furnace operation. The corrections which are made to the pyrometer readings of slab radiation are made in a manner and by means not found in the prior art patent.
U.S. Pat. No. 2,846,882 of William T. Gray discloses use of pyrometers receiving radiation from a workpiece and from a reference for a corrected measurement to control the heat applied to the work. Such two pyrometer systems are known in the prior art but the prior art does not show the correction or series of corrections that are made in the present invention to obtain accuracy not readily found in prior art apparatus.
U.S. Pat. No. 3,057,200 of John G. Wood discloses pyrometer detectors of radiation from an object and from a reference and also mention the concept of compensating for distances involved. Such a concept is involved in obtaining true slab temperature in the present invention but this patent still does not describe the aspects of measurement as found in the present invention.
Further background material concerning radiation detectors and attempts to increase the accuracy of their reading is discussed in the background material of the patent of Donald S. Michael, Patent No. 4,005,605. From this background material it is apparent that prior art accuracy was not as good as required and the apparatus and method of the present invention is an attempt to obtain such accuracy that allows the best use of pyrometers in one of their specialized uses of determining true slab temperature of such slab in a reheat furnace.